A novel type of arylsulfate sulfotransferase (ASST) from a predominant human intestinal bacterium catalyzes the stoichiometric transfer of a sulfate group from phenolic sulfate esters to phenols. We clarified that polyphenols were better substrates of this enzyme than the corresponding glycosides. Additionally, a coumarin derivative, esculetin, was sulfated by ASST at the 6-position to give 6-monosulfate. Therefore, ASST is more useful for the preparation of sulfated polyphenols at their specific hydroxyl groups and would play an important role in the metabolism of phenolic compounds in vegetable food and traditional medicines.